The aim of this research project is to do a pilot study to test a new pharmacologic treatment to increase the bone mass in women with vertebral crush fractures from postmenopausal osteoporosis. The long term objective is to reduce in the number of fractures in symptomatic women. Previous studies have shown that bone remodeling can be increased with inorganic phosphate by causing a mild secondary hyperparathyroidism. This proposal will extend that work with the hypothesis that, in patients with increased bone turnover, net bone formation can be induced by shortening the life span and/or activity of osteoclasts with the intermittent administration of synthetic salmon calcitonin. Trabecular and cortical bone mass will be measured in the distal radius using computerized axial tomography (CAT) scanning. Dual photon absorptiometry will be used to measure mineral content in the same area. Quantitative histomorphometry of the iliac crest will be done after double labeling with tetracycline. Hand x-rays will be taken using fine-grain industrial film to measure combined cortical thickness and intracortical resorption. Lateral spine films will be used to assess the number of vertebral fractures. The subjects will be randomized to a treatment group receiving the combination of oral phosphate 500 mg t.i.d. and synthetic salmon calcitonin 50 MRC units twice weekly or synthetic salmon calcitonin 50 MRC units twice weekly alone. They will be followed during a 1-year course of treatment.